Now UCI researchers think metabolism may join the ranks of other bodily functions that act in a cyclical manner following the body's internal clock.

Mice used in the study were kept in 12 hours of light and darkness, with tissue samples taken every six hours. The mice revealed periods of greater activity in certain metabolites — chemicals created by metabolism essential for cell health and growth — according to the university.

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"Recent studies reveal that a distorted circadian cycle [or changes in the body that are every 24 hours] can lead to aberrations in metabolism, producing symptoms such as obesity, insulin resistance and others consistent with the metabolic syndrome," the study said.

The research may have implications for people who stay up late, work night shifts or otherwise defy their body's internal clock that tells them to be restful during the night, said study co-author Kristin Eckel-Mahan, who said such behavior may create "more severe metabolic consequences then we originally thought."

The study could also have implications on drug therapy and tailoring diets, she said.

"We think it has a lot of human impact," Eckel-Mahan said. "We hope this will give us a better idea of why disturbances in circadian rhythm can cause metabolic disorders."

The creation of artificial "natural" lighting and other advents of the modern world work against the rhythms that control so many bodily functions, Eckel-Mahan said.

The immediate takeaway? Get a good's night rest — or at least relax during the dark hours of the day.